DE1443588C - Process for separating naphthalene hydrocarbons from mixtures containing Benzolkohlenwas by extraction - Google Patents

Description

1 2

The invention relates to a method for on the one hand a mixture of hydrocarbons in the

Separate naphthalene hydrocarbons from ben- non-polar solvents from the process

zolocarbons containing mixtures by withdrawn or better in the first extraction

Extraction is conducted by means of a solvent pair from an output batch to be supplied,

polar solvent and a saturated alipha- 5 Instead, the two solvents

tables hydrocarbon. used simultaneously in an extraction system

In the case of the process of the invention, the polar tradable mixtures are at least one solvent at one end of the system and the non-polar naphthalene hydrocarbon and at least one benzene solvent are fed to the other end, so that the two hydrocarbons are present. In addition, solvents can be run in countercurrent, with the charge to be treated, for example still alicyclic hydrocarbons, being introduced in between. Contain paraffin and / or olefin hydrocarbons. On the one hand, an extract is drawn off that is almost. The method of the invention is particularly suitable - the total naphthalene hydrocarbons of the discovery for the treatment of fractions which contain from the gangue charge in solution, on the other hand a rafficatalytic or thermal cracking originate from the other constituents of the starting charge or from the catalytic reforming of the heavy ones in the nonpolar one Contains solvent in solution.
Fractions from the pyrolysis of paraffins are used as a non-polar solvent as an aliphatic product or coal tar. Paraffinic hydrocarbon with at least 3 carbon atoms

There is already a process for liquid-liquid or a mixture of such hydrocarbons verExtraktion of naphthalene hydrocarbons (Naph- 20 uses, for example propane, n-heptane and n-dodethalin, «- and / 5-methylnaphthalene) from mixtures can aliphatic known, which in addition paraffins, olefins, aromatic solvents remain in a wide range of moles ^ and naphthenes. The known kular weight ranges are the same, for example no naphthalene-dissolving compounds are used, namely a noticeable difference between n-dodecane and alcohols, alkylene glycols, polyalkylene glycols and n-heptane.

the ethers of these alcohols and glycols to which water comes The choice of polar solvent can be added. Disadvantageously, it must be of crucial importance. It has to be at the same time at elevated temperatures and pressures and under excellent solution properties for naphthalene addition a protective gas (nitrogen, carbon monoxide) hydrocarbons and an excellent seleczur Avoid the action of oxygen on 30 activity for these hydrocarbons against the the solvent used in each case. combine with other aromatic hydrocarbons.

The object of the invention is to overcome these disadvantages. The used in the method of the invention

avoid and teach a process, which polar solvents are heterocyclic five-membered

in addition, with a considerably smaller amount of compounds that are obtained at
of valuable polar solvent, based on 35

the same amount to be treated mixture, from a) the esterification of a dicarboxylic acid with a

comes. Diol- (1,2) or with an epoxy; to such

This is achieved with a method of the above-mentioned solvents include, for example, the Alrissene type, which according to the invention is characterized by kylencarbonate, such as ethylene carbonate and Progek characterized in that the extraction is carried out with a 4 ° pylene carbonate, or its halogen-substituted heterocyclic five-membered ring compound as polar derivatives, such as chloropropylene carbonate , and solvents, preferably with an alkylene b) the internal esterification of a γ-oxycarboxylic acid; carbonate, a γ-lactone or a γ-lactam, such solvents include z. B. geTemperaturen below 125 ⁰ C carries out. In a saturated and unsaturated γ-lactone and its (( preferred embodiment of the invention contains 45 methyl derivatives, such as γ-butyrolactone, γ-Vada's polar solvent less than 15% by weight Ierolactone, γ-crotonolactone, and
percent water. c) the formation of internal amides in y-amino

The method of the invention can be applied to different acids; belong to such solvents

borrowed way. Example - for example pyrrolidone (2) and its higher

the polar solvent and the ali- 5 ° alkyl-substituted derivatives,
phatic hydrocarbon, which is considered to be non-polar

Solvent acts in two successive ways. It is known that these compounds dissolve

Liquid-liquid extractions are used for aromatic hydrocarbons and agents

will. In the first extraction, this will cause them to extract the same from their mixtures

trading hydrocarbon mixture with the polar 55 being used with aliphatic hydrocarbons

Solvent brought into contact in countercurrent. the can. However, it was not previously known that

On the one hand, there is a raffinate that is attached to naph- these compounds primarily to the naphthalene-

thaline hydrocarbons is poor, on the other hand, hydrocarbons are affine while their affinity

Extract that contains almost the entire naphthalene fraction of the benzene hydrocarbons, which is much lower

Contains starting mixture. The second extraction is 60. Nor was it known to have these remarkable

this extract is used in countercurrent with the non-valuable property for the selective separation of the naphtha

brought into contact with a polar solvent, which separates thaline hydrocarbons from the other aromatic

displaced the other hydrocarbons and exploit the table hydrocarbons, taking these

Naphthalene hydrocarbons in the extract con- centrate either of two types of hydrocarbons

triert. This second extraction results in a 65 alone or in a mixture with other hydrocarbons

enriched extract from which the naphthalene substances can be present. ·

hydrocarbons and the polar solvent. For example, in the table below are

be separated by suitable means, other - for comparison, the distribution measured at 25 ° C

coefficients. (Ka: Κχ = distribution coefficient of a benzene or naphthalene hydrocarbon, ie ratio of the concentration in moles per liter of the substance in the polar solvent to its concentration in moles per liter in the non-polar solvent) or selectivities (ß = KnIK, \) for the two solvents ! - Propylene carbonate and γ-ButyroIacton - and given for some known solvents from the family of glycols and glycol ethers. It turns out that the solvents of the process of the invention have higher partition coefficients than the other solvents with the same selectivity. In practice, this results in a considerable saving in the polar solvent to be used, which in comparison to the non-polar solvent is more expensive and, above all, its recovery is much more expensive.

The extraction can be carried out with solvents that are not absolutely anhydrous. The Adding water increases the selectivity of the solvent in all cases, but decreases it Solution performance. Preferably less than 15 weight percent water is used, generally 5 to 10 percent by weight. The table shows the effect achieved with the addition of water 10 percent by weight. The water can be added to the solvent all at once. However, it is in the generally more advantageous when working with two successive extractions for the first

ίο extraction - the extraction of the Naphthalinkohlenwasserstoffe - progressively add anhydrous polar solvent to be used and the water in the subsequent refining of the extract obtained with the aid of the non-polar solvent, until the above limits are reached; or when working with simultaneous use of both solvents, to introduce the water at different points of the extraction column between the bottom and the point of application of the batch to be treated.

Distribution coefficient K and selectivity β for various polar solvents at 25 ^° C

Polar
solvent

Weight percent

Water in
solvent

Distribution coefficient K

Benzene HC

Naphthalene HC

C ₁₀

K _n

Selectivity β

Naphthalenes / benzenes

C ", / C ₁₀ ! C _n IC ₁ ,,

β = KsIKa : β ' = K _n -IK

Propylene carbonate i

y-butyrolactone j

Diethylene glycol |

Triethylene glycol j

Carbitol '... {

0
10

0
10

0
10

0
10

0
10

1.82
1.10

2.96
1.38

1.00
0.332

0.788
0.404

1.35
0.80

2.00
0.94

0.4
0.155

0.69
0.210

0.594
0.246

5.70
6.32

4.92

5.52

7.51
9.20

4.73
6.11

4.22
4.60

3.33
3.76

5.0
5.2

5.19
5.84

3.58
3.42

The values of K indicate the ratio of the concentration in percent by volume in the polar solvent phase to the concentration in the non-polar solvent phase, here n-dodecane, in infinite dilution.

In the practice of the invention, the amount of polar solvent to be used in relation to the hydrocarbon mixture to be treated depends to a large extent on its composition. If naphthalene and methylnaphthalenes are to be extracted from a relatively poor mixture (for example with a total content of polycyclic hydrocarbons of below 30 ° / ₀ ), which contains paraffin, olefin hydrocarbons and alkylbenzenes and one works approximately at ambient temperature, then the Working with two-stage extraction, use 0.3 to 3.0 parts by volume of polar solvent per part by volume of batch to be treated, preferably 0.7 to 1.2 parts by volume of polar solvent per part by volume of batch. If both solvents are used at the same time, these values are 0.5 to 3.5 parts by volume of polar solvent per part by volume of batch, and a volume ratio of 1 to 1.8 is preferably used. With the known solvents from the glycol family, the amounts of the polar solvent to be used per part by volume of batch are two to three times higher under the same conditions.

The proportion of non-polar solvent to be used with the polar solvent, d. H. of paraffinic hydrocarbons, is given by the volume ratio of polar to non-polar solvent, which is between 0.3 and 2.4, preferably between 0.7 and 1.2 is when extraction is carried out in two stages. When working with simultaneous exposure to both solvents the ratio is between 1.5 and 7.0, preferably between 2.5 and 4.0.

If the batch to be treated is very rich in naphthalene hydrocarbons or poor in benzene hydrocarbons, or if it is not necessary to fully extract the naphthalenes, then of course the amount of polar solvent used per batch unit can be greatly reduced, and the volume ratio of polar solvent to batch may ° / ₀ assume the values given above up to 60 to 70 wt.

The separation of the naphthalene hydrocarbons from the extract and the recovery of the polar solvents can be carried out with all known means, for example by

Distillation and / or aqueous extraction take place. The non-polar solvent can be obtained by distillation to be recovered.

The polar solvent is preferably extracted with water, optionally after a preceding one Distillation. The subsequent dehydration of the solvent takes place in a known manner. When the solvent is extracted by water, it may be necessary to remove the naphthalene hydrocarbons to be diluted with a light hydrocarbon in order to separate the naphthalene hydrocarbons containing oily layer from the aqueous phase to ease the polar Contains solvent. The extracted naphthalenes have a density that is too close to that of the Water to enable rapid decantation, and there is also a risk that they will crystallize after the solvent has been stripped off. However, the paraffin solvent is often sufficient in the naphthalene hydrocarbon extract soluble so that this additional dilution is not necessary.

The following examples serve to illustrate the invention.

example 1

A hydrocarbon mixture of the following composition is assumed:

n-dodecane 60 percent by weight

Alkylbenzene (diirol) 20 percent by weight

Naphthalene 5 percent by weight

1-methylnaphthalene 15 percent by weight

At a temperature of 20'C, 80 g (approx. 100 cm ^-1 ) of the mixture are vigorously ^{stirred with 50 cm -1} propylene carbonate. A first lower layer, an extract rich in polar solvent, is decanted. The top layer, the raffinate, is ^{treated again with 50 cm 3 of} propylene carbonate. A second extract is separated and added to the first. The entire extract is subjected to four successive washes with 25 cm ^{3 of} n-heptane each time. The washed extract is then diluted with one liter of water. 5.68 g of an oily substance floating above with the following composition are separated:

n-dodecane 0 percent by weight

Alkylbenzene 6.8%

Naphthalene -8.4%

1-methylnaphthalene. 64.8%

The concentration of naphthalene hydrocarbons. that in the starting mixture is 20 percent by weight so increases to 93.2 percent by weight in the final extract, and 33.1 percent of the in the amount of naphthalene hydrocarbons present in the starting mixture won.

Example 2

The procedure is as described in Example 1, but - / - Butyrolactone is used instead of propylene carbonate used as a polar solvent.

80 g of the specified starting mixture are treated in two successive stages, each with .42.5 cnr ¹ anhydrous j'-butyrolactone at a temperature of 20 C. The two combined extracts are then ^{subjected to four successive washes with 25 cm 3 of} n-heptane each time. ^{300 cm 3 of} water are added to the extract and 7.86 g of an oily phase of the following compositions are separated off:

n-dodecane 0.0 percent by weight

Alkylbenzene (Durol) 13.4%

Naphthalene 25.8%

ίο 1-methylnaphthalene 60.7%

The concentration of naphthalene hydrocarbons in the starting mixture is 20 percent by weight was, so increases to 86.5 percent by weight in the last extract. It becomes 42.5% of the naphthalene hydrocarbons obtained that were present in the starting product.

Eg 1 3

It is treated the desulfurized than going 200-240 ⁰ C fraction of a catalytic gas oil having the following composition in volume percent:

Saturated hydrocarbons 31.60

Aromatic hydrocarbons 42.1

Naphthalene 5.2

Methylnaphthalene 21.1

Thionaphthen traces

This fraction is added to the third tray from the bottom of an extraction tower operating at 25 ° C abandoned five floors, the top side continuously as a polar solvent j'-ButyroIacton (2 volumes Per volume of treated batch) and n-dodecane continuously on the foot side (2 volumes per volume of treated Batch) can be fed in as a paraffinic solvent.

. After the solvents have been removed and recovered, 100 parts by volume are treated Batch essentially 25 parts by volume of extract and 75 parts by volume of raffinate obtained, which the following Composition (in percent by volume):

Saturated hydrocarbons. Aromatic hydrocarbons

naphthalene

Methylnaphthalene

Raffinate extract

1.2 21.1

16.0 61.7

41.7

49.2

Thus 74% of the amount of all naphthalene hydrocarbons are obtained from the treated batch, with a total concentration of 77.7 percent by volume in the extract.

Example 4

The procedure is as described in Example 1, but instead of propylene carbonate, chloropropylene carbonate is used used.

80 g of the specified starting mixture are ^{treated in two successive stages with 50 cm 3 of} anhydrous chloropropyl carbonal each at a temperature of 20 ° C. The two combined extracts then graze four consecutive

subjected to washes with 25 cm ^{3 of} n-heptane each time. ^{1500 cm 3 of} water are added to the extract finally obtained. 6.55 g of an oily phase of the following composition are separated off:

n-dodecane 0.0 percent by weight

Alkylbenzene (Durol) 9.8%

Naphthalene 26.4%

1-methylnaphthalene 63.8%

The concentration of naphthalene hydrocarbons in the starting mixture is 20 percent by weight was increased to 90.2 percent by weight in the final extract. 36.9% of that contained in the starting product Naphthalene hydrocarbons are obtained.

Example 5

The treatment described in Example 1 is with γ-valerolactone instead of propylene carbonate as polar solvent carried out.

80 g of said starting mixture are treated ^{in two successive steps with 35 cm 3 of} anhydrous γ-valerolactone each at a temperature of 20 ^{° C.} The two combined extracts are then ^{subjected to four successive washes with 25 cm 3 of} n-heptane each time. 300 cm of water are added to the extract finally obtained. 7.70 g of an oily phase of the following compositions are separated off:

n-dodecane 0.0 percent by weight

Alkylbenzene (Durol) ..... 8.8%

Naphthalene 25.0%

1-methylnaphthalene 66.2%

The concentration of naphthalene hydrocarbons in the starting mixture is 20 percent by weight amounts to 91.2 percent by weight in the final extract. 43.8% of the naphthalene hydrocarbons contained in the starting product are recovered.

B e i s ρ i e 1 6

The procedure is as described in Example 1, but instead of propylene carbonate as polar Solvent methylpyrrolidone- (2) used.

80 g of the starting mixture mentioned are ^{treated in two successive steps with 35 cm 3 of} anhydrous methylpyrrolidone- (2) each at a temperature of 20.degree. The two combined extracts are then ^{subjected to four successive washes with 25 cm 3 of} n-heptane each time. ^{500 cm 3 of} water are added to the extract finally obtained. 6.72 g of an oily phase of the following composition are separated off:

n-dodecane 0.0 percent by weight

Alkylbenzene (Durol) 18.0%

Naphthalene 21.8%

1-methylnaphthalene 60.2%

The concentration of naphthalene hydrocarbons in the starting mixture is 20 percent by weight was 82.0 percent by weight in the final extract. 34.4% of that contained in the starting product Naphthalene hydrocarbons are obtained.

Claims (2)

Patent claims: Ϊ. Process for separating naphthalene hydrocarbons from mixtures containing benzene hydrocarbons by extraction by means of a solvent pair from a polar solvent and a saturated aliphatic hydrocarbon, characterized in that the extraction is carried out with a heterocyclic five-membered ring compound as polar solvent, preferably an alkylene carbonate, a γ-lactone or a γ -Lactam, at temperatures below 125 ⁰ C performs. , 2. The method according to claim 1, characterized in that the polar solvent is less contains more than 15 percent water by weight .. 009 684/47